1. Field of the Invention:
The present invention relates to a current sensor for welder conductor for detecting a current flowing through a welder conductor such as cables, shunts, movable arms, and fixed arms, etc., and for thereby informing an operator of whether or not the current so detected is above a prescribed value.
2. Description of the Prior Art:
A welding current should fall in general within a prescribed range for assuring satisfactory welding operation independently of the thicknesses of articles to be welded and material qualities thereof, etc. However, such a current flowing through the welder conductor changes depending on the degree of wear of a welder tip, the rate of breakdown of electric wires, the degree of cooling for the conductor, varieties of supply voltage, etc. It is therefore needed to monitor at all times how much the current is conducted through the welder conductor.
Some current sensors to detect such a welder conductor current are known. One example is shown in FIG. 7 wherein a current is indirectly picked up through a high permeability toroidal core 21, which is formed by winding plural times a coil around a cable 20 through which the current is conducted, and furthermore a light emitting diode (LED) 22 is connected across terminals of the toroidal core. Another example is shown in FIG. 8 wherein a sensor circuit is connected between the terminals of the toroidal core.
These circuits however have some drawbacks. Namely, with the toroidal core 21 of FIG. 7 employed as a welder conductor, the LED permits an AC current to be directly conducted therethrough, and hence it is discontinuously lighted with the result that it is difficult to know a current level because of the indefiniteness of the brightness of light emitted therefrom. In addition, the situation arrangement of FIG. 8 necessitates a separate power source for the sensor circuit.